Understanding How Plant Hardiness Zones Affect Plant Growth

PLANT GROWTH FACTORS

What is meant by USDA Plant Hardiness Zone Map?

If gardening is a new experience for you, this may seem a bit confusing. However, this is not as hard to understand as it sounds.

The zones refer to the climate in which you live. All plants have certain zones in which they thrive. The temperatures are one of the factors. The extremes in cold and heat affect the way plants grow.

Plant hardiness Maps

The Plant hardiness zones in North America are decided by the United States Department of Agriculture (USDA). This map was last updated in 1990 and used records for the types of weather experienced across the U.S. from 1974 to 1986.

This is the standard used for measuring the hardiness of plants across the U.S. The agriculture department in Canada has also developed their own map for the hardiness zones in Canada.

There are 11 zones with zone 1 having the coldest temperatures and zone 11 the warmest. Every plant has a zone or zones in which they can survive. Some plants can only grow and produce in certain temperatures so they will only be specific to those zones. Some plants will be fine at a certain zone and under that zone. If this is the case the plant will say for example, zone 6. If there are only certain zones the plant will grow and thrive in the instructions will say zones 3- 8.

This is why it is extremely important to pay attention to the recommended zones. If you just plant something and never check to see where it is best to do so, odds are this plant may not do well, produce anything or even survive.

Zones Use Several Factors

The zone in which a plant will fare well is not only contingent upon temperature but it is also dependent upon other factors. The length of the day, wind conditions, heat and humidity are all factors that will determine if a plant will do well in your area. This is why tests are conducted to see what plants do better in certain areas.

The plant hardiness zone, as it is often called will also include the soil and local climates. There are several areas that may be in the same zone but will have totally different climates. There are also microclimates - these are climates that are only specific to a small area.

Sunset Zones

There are other zones that are considered as well. The western part of the United States uses a sunset zone. This was created over 40 years ago.

Sunset Magazine started this method of determining what grows best here. In this area, most nurseries use this standard for plant hardiness.

Not only does this method use the temperatures, but they also figure in the high temperature in the summer, how long the growing season lasts, the amount of rainfall and the humidity of the area.

Although these are utilized more in the Midwest they also use the USDA guidelines as well.

While it is important to rely on plant hardiness zones for much of what we plant, there are also other factors that will have to be taken into consideration as well. Your garden is unique to your area and what will and will not grow is basically a trial and error process.

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